Non-aqueous secondary batteries, including lithium ion secondary batteries, provide high voltage and high capacity, and therefore are widely used as power sources for various portable devices. Moreover, in recent years, their applications have expanded to medium- and large-size applications such as power tools including electric tools, electric vehicles, and electric bicycles.
In particular, there are demands for a battery having a higher capacity for use in cellular phones, game machines, and the like that are increasingly smaller and provided with multiple functions, and research and development on an electrode active material that demonstrates a high charge and discharge capacity as a means thereof is on progress. Especially, as an ingredient of a negative electrode active material, attention has been given to materials such as silicon (Si) and tin (Sn) that can store and release larger amounts of lithium (ions) in place of a carbon material such as graphite used in conventional non-aqueous secondary batteries. Among others, SiOx, which has a structure in which ultrafine Si particles are dispersed in SiO2, has been reported as also having features such as excellent load characteristics (see Patent Documents 1 and 2).
However, it is known that since the aforementioned SiOx undergoes large volume expansion and contraction associated with a charge and discharge reaction, particles are pulverized for every charge and discharge cycle of a battery, resulting in problems such as an irreversible capacity increase due to a reaction between Si precipitated on the surface and a non-aqueous electrolyte solution, and battery expansion due to charge and discharge. Also, SiOx has a fine structure, and thus some effect is observed on improvement of the load characteristics of a battery, but there is still room for improvement on the point that SiOx itself is a poorly conductive material.
In view of this situation, techniques have been proposed of suppressing the volume expansion and contraction of SiOx, which accompanies a charge and discharge reaction, by limiting SiOx utilization, improving load characteristics by coating the SiOx surface with a conductive material such as carbon, and improving the charge and discharge cycle characteristics of a battery using a non-aqueous electrolyte solution to which a halogen-substituted cyclic carbonate (such as 4-fluoro-1,3-dioxolan-2-one), vinylene carbonate, or the like is added (see Patent Document 3).